Research has continued to develop golf balls which allow a golfer to put a lot of spin when hitting the ball do not wear out easily by repeated hitting, and achive an improved flight distance. In general, a golf ball is composed of a core and a cover surrounding the core, and particularly, the cover of the golf ball is a part that receives a direct hit, wherein hardness, wear resistance, and scuff resistance are important, and excellent restitution characteristics for hitting as well as flexible and soft physical properties are also required.
A material for a golf ball cover recently used may include polyurethane which is cast by a casting method, wherein the polyurethane has excellent elasticity to provide a good sense of hit when hitting and increases the number of rotations of the golf ball to allow the golf ball to fly further. Also, since the polyurethane has elasticity, flexibility, and soft physical properties and has excellent wear resistance and scuff resistance against hitting, the polyurethane has been recognized for its value in the premium golf ball market and its market has also tended to gradually expand. For example, Korean Patent Application Laid-open Publication No. 2014-0092575 discloses a resin composition including a chain extender, isocyanate, polyol, organic peroxide, and a montan-based wax, as a polyurethane-based resin composition which may be used as a golf ball cover.
However, despite the above-described advantages, since the polyurethane is a polymer that sensitively reacts to a change in temperature, physical properties may change under low and high temperature conditions due to seasonal changes. As a result, even if a hit is applied with the same intensity, there is a part in which the number of rotations and restitution characteristics may vary depending on season or surrounding environmental influences.
Thus, the present inventors devised a resin composition for a polyurethane golf ball cover, which may have a higher number of rotations when being hit, by minimizing changes in physical properties of a ball due to seasonal temperature changes and further improving modulus properties, thereby leading to the completion of the present invention.